Catbird, welcome to Pond Boss.
Like Ken(Catmandoo in the funny papers) says, I'll bet we can get someone out there to look it over.
The green is plankton and it has to have a source of nutrients to get started and thrive. Do you have any runoff from cattle manure or anything like that? Maybe from a neighbor? Do you have any other vegetation in the pond?
The well water, to me, is suspect #1. Think about this. During the winter when you don't pump, the pond clears. Add water and you get a massive algae bloom. Have the well water tested.
It might be that you have too many fish and, as Bill Cody says, fish swim in their own toilet. Thus, they can create their own fertilizer bloom under extreme circumstances.
Small, skinny bass and large bluegills usually says that the pond is bass heavy meaning that the small bass eat the small bluegills before they get a chance to get large enough to feed any larger bass. Thus the cycle continues and this is very common. However, I have no answer to the fathead proliferation in this case.
Disclaimer: Ken is certifiably nuts. And, at darn near 70 YOA, I am senile with ADHD and dementia. Just ask my Wife.
